cppcheck/lib/checkassignif.cpp

333 lines
13 KiB
C++

/*
* Cppcheck - A tool for static C/C++ code analysis
* Copyright (C) 2007-2014 Daniel Marjamäki and Cppcheck team.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
//---------------------------------------------------------------------------
// Check for assignment / condition mismatches
//---------------------------------------------------------------------------
#include "checkassignif.h"
#include "symboldatabase.h"
//---------------------------------------------------------------------------
// Register this check class (by creating a static instance of it)
namespace {
CheckAssignIf instance;
}
void CheckAssignIf::assignIf()
{
if (!_settings->isEnabled("style"))
return;
for (const Token *tok = _tokenizer->tokens(); tok; tok = tok->next()) {
if (tok->str() != "=")
continue;
if (Token::Match(tok->tokAt(-2), "[;{}] %var% =")) {
const Variable *var = tok->previous()->variable();
if (var == 0)
continue;
char bitop = '\0';
MathLib::bigint num = 0;
if (Token::Match(tok->next(), "%num% [&|]")) {
bitop = tok->strAt(2).at(0);
num = MathLib::toLongNumber(tok->next()->str());
} else {
const Token *endToken = Token::findsimplematch(tok, ";");
// Casting address
if (endToken && Token::Match(endToken->tokAt(-4), "* ) & %any% ;"))
endToken = nullptr;
if (endToken && Token::Match(endToken->tokAt(-2), "[&|] %num% ;")) {
bitop = endToken->strAt(-2).at(0);
num = MathLib::toLongNumber(endToken->previous()->str());
}
}
if (bitop == '\0')
continue;
if (num < 0 && bitop == '|')
continue;
assignIfParseScope(tok, tok->tokAt(4), var->declarationId(), var->isLocal(), bitop, num);
}
}
}
/** parse scopes recursively */
bool CheckAssignIf::assignIfParseScope(const Token * const assignTok,
const Token * const startTok,
const unsigned int varid,
const bool islocal,
const char bitop,
const MathLib::bigint num)
{
bool ret = false;
for (const Token *tok2 = startTok; tok2; tok2 = tok2->next()) {
if (Token::Match(tok2->tokAt(2), "%varid% %cop% %num% ;", varid) && tok2->strAt(3) == std::string(1U, bitop)) {
const MathLib::bigint num2 = MathLib::toLongNumber(tok2->strAt(4));
if ((bitop == '&') && (0 == (num & num2)))
mismatchingBitAndError(assignTok, num, tok2, num2);
}
if (Token::Match(tok2, "%varid% =", varid)) {
if (Token::Match(tok2->tokAt(2), "%varid% %cop% %num% ;", varid) && tok2->strAt(3) == std::string(1U, bitop)) {
const MathLib::bigint num2 = MathLib::toLongNumber(tok2->strAt(4));
if ((bitop == '&') && (0 == (num & num2)))
mismatchingBitAndError(assignTok, num, tok2, num2);
}
return true;
}
if (Token::Match(tok2, "++|-- %varid%", varid) || Token::Match(tok2, "%varid% ++|--", varid))
return true;
if (Token::Match(tok2, "[(,] &| %varid% [,)]", varid)) {
unsigned int argumentNumber = 0;
const Token *ftok;
for (ftok = tok2; ftok && ftok->str() != "("; ftok = ftok->previous()) {
if (ftok->str() == ")")
ftok = ftok->link();
else if (ftok->str() == ",")
argumentNumber++;
}
ftok = ftok ? ftok->previous() : nullptr;
if (!(ftok && ftok->function()))
return true;
const Variable *par = ftok->function()->getArgumentVar(argumentNumber);
if (par == nullptr || par->isReference() || par->isPointer())
return true;
}
if (tok2->str() == "}")
return false;
if (Token::Match(tok2, "break|continue|return"))
ret = true;
if (ret && tok2->str() == ";")
return false;
if (!islocal && Token::Match(tok2, "%var% (") && !Token::simpleMatch(tok2->next()->link(), ") {"))
return true;
if (Token::Match(tok2, "if|while (")) {
if (!islocal && tok2->str() == "while")
continue;
// parse condition
const Token * const end = tok2->next()->link();
for (; tok2 != end; tok2 = tok2->next()) {
if (Token::Match(tok2, "[(,] &| %varid% [,)]", varid)) {
return true;
}
if (Token::Match(tok2,"&&|%oror%|( %varid% %any% %num% &&|%oror%|)", varid)) {
const Token *vartok = tok2->next();
const std::string& op(vartok->strAt(1));
const MathLib::bigint num2 = MathLib::toLongNumber(vartok->strAt(2));
const std::string condition(vartok->str() + op + vartok->strAt(2));
if (op == "==" && (num & num2) != ((bitop=='&') ? num2 : num))
assignIfError(assignTok, tok2, condition, false);
else if (op == "!=" && (num & num2) != ((bitop=='&') ? num2 : num))
assignIfError(assignTok, tok2, condition, true);
}
}
bool ret1 = assignIfParseScope(assignTok, end->tokAt(2), varid, islocal, bitop, num);
bool ret2 = false;
if (Token::simpleMatch(end->next()->link(), "} else {"))
ret2 = assignIfParseScope(assignTok, end->next()->link()->tokAt(3), varid, islocal, bitop, num);
if (ret1 || ret2)
return true;
}
}
return false;
}
void CheckAssignIf::assignIfError(const Token *tok1, const Token *tok2, const std::string &condition, bool result)
{
std::list<const Token *> locations;
locations.push_back(tok1);
locations.push_back(tok2);
reportError(locations,
Severity::style,
"assignIfError",
"Mismatching assignment and comparison, comparison '" + condition + "' is always " + std::string(result ? "true" : "false") + ".");
}
void CheckAssignIf::mismatchingBitAndError(const Token *tok1, const MathLib::bigint num1, const Token *tok2, const MathLib::bigint num2)
{
std::list<const Token *> locations;
locations.push_back(tok1);
locations.push_back(tok2);
std::ostringstream msg;
msg << "Mismatching bitmasks. Result is always 0 ("
<< "X = Y & 0x" << std::hex << num1 << "; Z = X & 0x" << std::hex << num2 << "; => Z=0).";
reportError(locations,
Severity::style,
"mismatchingBitAnd",
msg.str());
}
static void getnumchildren(const Token *tok, std::list<MathLib::bigint> &numchildren)
{
if (tok->astOperand1() && tok->astOperand1()->isNumber())
numchildren.push_back(MathLib::toLongNumber(tok->astOperand1()->str()));
else if (tok->astOperand1() && tok->str() == tok->astOperand1()->str())
getnumchildren(tok->astOperand1(), numchildren);
if (tok->astOperand2() && tok->astOperand2()->isNumber())
numchildren.push_back(MathLib::toLongNumber(tok->astOperand2()->str()));
else if (tok->astOperand2() && tok->str() == tok->astOperand2()->str())
getnumchildren(tok->astOperand2(), numchildren);
}
void CheckAssignIf::comparison()
{
if (!_settings->isEnabled("style"))
return;
// Experimental code based on AST
for (const Token *tok = _tokenizer->tokens(); tok; tok = tok->next()) {
if (Token::Match(tok, "==|!=")) {
const Token *expr1 = tok->astOperand1();
const Token *expr2 = tok->astOperand2();
if (!expr1 || !expr2)
continue;
if (expr1->isNumber())
std::swap(expr1,expr2);
if (!expr2->isNumber())
continue;
const MathLib::bigint num2 = MathLib::toLongNumber(expr2->str());
if (num2 < 0)
continue;
if (!Token::Match(expr1,"[&|]"))
continue;
std::list<MathLib::bigint> numbers;
getnumchildren(expr1, numbers);
for (std::list<MathLib::bigint>::const_iterator num = numbers.begin(); num != numbers.end(); ++num) {
const MathLib::bigint num1 = *num;
if (num1 < 0)
continue;
if ((expr1->str() == "&" && (num1 & num2) != num2) ||
(expr1->str() == "|" && (num1 | num2) != num2)) {
const std::string& op(tok->str());
comparisonError(expr1, expr1->str(), num1, op, num2, op=="==" ? false : true);
}
}
}
}
}
void CheckAssignIf::comparisonError(const Token *tok, const std::string &bitop, MathLib::bigint value1, const std::string &op, MathLib::bigint value2, bool result)
{
std::ostringstream expression;
expression << std::hex << "(X " << bitop << " 0x" << value1 << ") " << op << " 0x" << value2;
const std::string errmsg("Expression '" + expression.str() + "' is always " + (result?"true":"false") + ".\n"
"The expression '" + expression.str() + "' is always " + (result?"true":"false") +
". Check carefully constants and operators used, these errors might be hard to "
"spot sometimes. In case of complex expression it might help to split it to "
"separate expressions.");
reportError(tok, Severity::style, "comparisonError", errmsg);
}
extern bool isSameExpression(const Token *tok1, const Token *tok2, const std::set<std::string> &constFunctions);
static bool isOverlappingCond(const Token * const cond1, const Token * const cond2, const std::set<std::string> &constFunctions)
{
if (!cond1 || !cond2)
return false;
// same expressions
if (isSameExpression(cond1,cond2,constFunctions))
return true;
// bitwise overlap for example 'x&7' and 'x==1'
if (cond1->str() == "&" && cond1->astOperand1() && cond2->astOperand2()) {
const Token *expr1 = cond1->astOperand1();
const Token *num1 = cond1->astOperand2();
if (!num1) // unary operator&
return false;
if (!num1->isNumber())
std::swap(expr1,num1);
if (!num1->isNumber() || MathLib::isNegative(num1->str()))
return false;
if (!Token::Match(cond2, "&|==") || !cond2->astOperand1() || !cond2->astOperand2())
return false;
const Token *expr2 = cond2->astOperand1();
const Token *num2 = cond2->astOperand2();
if (!num2->isNumber())
std::swap(expr2,num2);
if (!num2->isNumber() || MathLib::isNegative(num2->str()))
return false;
if (!isSameExpression(expr1,expr2,constFunctions))
return false;
const MathLib::bigint value1 = MathLib::toLongNumber(num1->str());
const MathLib::bigint value2 = MathLib::toLongNumber(num2->str());
return ((value1 & value2) == value2);
}
return false;
}
void CheckAssignIf::multiCondition()
{
if (!_settings->isEnabled("style"))
return;
const SymbolDatabase* const symbolDatabase = _tokenizer->getSymbolDatabase();
for (std::list<Scope>::const_iterator i = symbolDatabase->scopeList.begin(); i != symbolDatabase->scopeList.end(); ++i) {
if (i->type != Scope::eIf || !Token::simpleMatch(i->classDef, "if ("))
continue;
const Token * const cond1 = i->classDef->next()->astOperand2();
const Token * tok2 = i->classDef->next();
while (tok2) {
tok2 = tok2->link();
if (!Token::simpleMatch(tok2, ") {"))
break;
tok2 = tok2->linkAt(1);
if (!Token::simpleMatch(tok2, "} else { if ("))
break;
tok2 = tok2->tokAt(4);
if (isOverlappingCond(cond1, tok2->astOperand2(), _settings->library.functionpure))
multiConditionError(tok2, cond1->linenr());
}
}
}
void CheckAssignIf::multiConditionError(const Token *tok, unsigned int line1)
{
std::ostringstream errmsg;
errmsg << "Expression is always false because 'else if' condition matches previous condition at line "
<< line1 << ".";
reportError(tok, Severity::style, "multiCondition", errmsg.str());
}